JEE 2022 | Class 12

JEE Important Chapter - Biomolecules

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Introduction to Biomolecules

Introduction to Biomolecules

Every living entity, from plants to mammals, is built up of small building components called cells. They are the tiniest fundamental units that make up our bodies, and they are made up of a variety of inorganic and organic chemicals. All carbon-containing substances found in living stuff are considered biomolecules.


Biomolecules are an important part of the JEE Main syllabus. We've covered all of the main aspects of biomolecules in this article, including what is biomolecules, types of biomolecules, the structure of biomolecules, previous year questions, practice questions, etc. This extensive biomolecules article will help you gain an edge over your competitors.  

Important Topics of Biomolecules

  • Chirality

  • Glucose 

  • Anomers

  • Cellulose

  • Sucrose

  • Fructose

  • Optical isomerism

  • Pyranose ring

  • Tollen’s Test

Important Concepts of Biomolecules

Pyranose ring 

Pyranose is a name that refers to saccharides that have a six-membered ring with five carbon atoms and one oxygen atom in their chemical structure.

Furanose ring

Four carbon and one oxygen atoms make up a furanose ring, with the anomeric carbon to the right of the oxygen.

Tollen’s test of sucrose

Only when aldehyde and hydroxy ketone are present does Tollen's test yield a positive result. There are no free aldehydes or hydroxy ketone in sucrose.

Tollen’s test of fructose and glucose

Because glucose has an aldehyde group on top, it passes the test, whereas fructose does not.

What are Biomolecules?

Biomolecules are organic chemicals that make up the very backbone of a cell in living creatures. Carbohydrates, lipids, and proteins, for example, could all be present in various quantities. All of these biomolecules serve important functions in the body and are produced there. Some examples of biomolecules are DNA, RNA, cellulose, and glucose.


While organic molecules can be made up of straight-chain carbons, they can also be made up of cyclic rings, branched chains, or a combination of these. They differ in terms of characteristics, chemical properties, and structures, which leads to differences in physical attributes like boiling and melting points, as well as water solubility. Biomolecules can be classified as hydrophilic or hydrophobic depending on their affinity for water.


Major Structural Elements of Biomolecules

The majority of biomolecules are organic compounds made up of only four components. The major structural elements of biomolecules are oxygen, carbon, hydrogen, and nitrogen. They account for 96 percent of the mass of the human body. However, several additional elements, such as biometals, are present in trace levels.


Classification of Biomolecules

Make sure you understand organic compounds and their properties before moving on to the next section of this biomolecule article. This will make it easier for you to comprehend the next things. The several types of biomolecules are discussed here.

Carbohydrates, proteins, nucleic acids, and lipids are the four main types of biomolecules. From these, the most abundant biomolecule on earth is carbohydrates.

1. Carbohydrates: Carbohydrates are polysaccharides that are the end products of the majority of our body's metabolic processes. They are the foundations of our metabolic apparatus, and their molecular structure is made up of several monosaccharides stacked on top of one another. Carbohydrates are abundant in most living cells, and it is safe to claim that these biomolecules represent the origin of life on our planet.

For example, cellulose is an essential component of plant cells, and it is normally stored as starch. Glucose, on the other hand, is the end product of photosynthesis, the process by which plants convert sunlight into food. Monosaccharides, disaccharides, and oligosaccharides are the three main types of saccharides. They're divided into groups based on the number of sugar molecules they contain.

Sucrose, cellulose, fructose, glucose, and dextrose are some of the most common sugars we encounter on a regular basis. You'll also learn about the three fundamental types of sugar-containing carbohydrates, namely monosaccharides, oligosaccharides, and disaccharides, in these biomolecules Class 12 notes.

  • Monosaccharides: They are the most basic carbohydrates and cannot be further hydrolyzed. They are present in the general chemical formulae of (CH2O)n. Ribose and glucose are examples of monosaccharides.

  • Oligosaccharides: These are complicated carbohydrates that break down into two to ten monosaccharide subunits. They are then subdivided into other categories. Stachyose and raffinose are two examples.

  • Disaccharides: Disaccharides are carbohydrates that break down into two monosaccharide molecules when hydrolyzed. Sucrose, for example, produces fructose and glucose. Maltose, on the other hand, releases two molecules of glucose when hydrolyzed.

2. Proteins: Proteins are organic substances that are abundant in our meals and are made up of amino acids. They are made up of long-chain monomers joined together by polypeptide bonds. As a result, proteins are also known as polypeptides.

3. Lipids: Fats, oils, steroids, phospholipids, and glycerol are all examples of hydrophobic substances. Lipids can have a variety of structures and properties depending on the ingredients. Fatty acids, for example, are composed of a single carboxyl group attached to a variable group or R. Saturated or unsaturated fatty acids can be found in these foods.

Furthermore, some lipids may contain phosphorus groups that are linked to the organic groups. Phospholipids are another name for them. Phospholipids are the fundamental components of a cell's plasma membrane.

4. Nucleic Acids: The smallest fundamental pieces of our genetic information, often known as genes, are made up of DNA and RNA building blocks. These are a combination of nitrogenous bases, sugar molecules, and a phosphate group that make up our bodies' genetic material.

Purines and pyrimidines are examples of heterocyclic compounds. Xanthine, caffeine, and nitrogenous bases like guanine and adenine are examples of purines. The product of nitrogenous bases forming chemical bonds with sugar molecules is known as a nucleoside. Nucleotides are formed when these molecules interact with phosphate groups (RNA, DNA).


Importance of Biomolecules

Biomolecules are essential for life since they assist organisms in growing, living, and reproducing. They aid the development of organisms ranging from single cells to sophisticated living beings such as humans by interacting with one another. Because of their shape and structure, they can be used for a variety of purposes.


Solved Examples/Problems from the Chapter: Biomolecules

1. Glucose or sucrose are soluble in water but cyclohexane or benzene (simple six-membered ring compounds) are insoluble in water - Explain.

Ans: Glucose and sucrose, respectively, have five and eight -OH groups. As a result, they're more likely to form hydrogen bonds with water molecules. Because their electronegativity differences are so small, cyclohexane and benzene are non-polar compounds. As a result, they are not water soluble.

Key Points to remember: Although carbon chains are naturally hydrophobic, the introduction of strong electronegative elements causes them to become hydrophilic due to the development of polarity in the molecules.


2. Where does the water present in the egg go after boiling the egg?

Ans: When an egg is cooked, the globular proteins (egg white albumin) coagulate (denature) into a rubbery, intractable mass. As it forms hydrogen bonds with the egg's water, this insoluble mass swallows it all.

Key Points to remember: Protein denaturation occurs at high temperatures.


Solved Problems of Previous Year Question from the Chapter: Biomolecules

1. The helical structure of a protein is formed by which bond?


(a) H-bond

(b) Peptide bond

(c) Dipeptide bond

(d) None of these

Ans: The correct answer is option a.


Helical structure of a protein


Trick: Certain folding patterns are caused by hydrogen bonding between amino groups and carboxyl groups in neighbouring regions of the protein chain.


2. Match the following:


Column I

Column II


(a) Beriberi


(b) Scurvy


(c) Cheilosis

Ascorbic Acid

(d) Convulsions



(a) (i)-(c), (ii)-(a), (iii)-(d), (iv)-(b)

(b) (i)-(c), (ii)-(d), (iii)-(a), (iv)-(b)

(c) (i)-(a), (ii)-(d), (iii)-(c), (iv)-(b)

(d) (i)-(d), (ii)-(b), (iii)-(a), (iv)-(c)

Ans: The correct answer is option a. 

Trick: Ascorbic acid protects and maintains the health of cells.

Riboflavin aids in the formation of red blood cells.

Thiamine aids the conversion of carbohydrates into energy in the body's cells.

Pyridoxine is a B vitamin that aids nerve activity.


3. Out of the following isomeric forms of uracil, which one is present in RNA?


Isomeric forms of uracil


Ans: The correct answer is option c. It is a heterocyclic compound with double bonded two oxygens. 

Trick: The chemical formula of uracil is C4H4N2O2.


Practice Questions

1. What products would be formed when a nucleotide from DNA containing

thymine is hydrolysed? (Ans: Thymine β-D-2-deoxyribose and phosphoric acid )

2. What are the hydrolysis products of sucrose? (Ans: Glucose and fructose)


Studying this Biomolecules Class 12 notes for JEE Main well in advance will go a long way toward ensuring you get the best rank. Students can get well-structured and accurate study notes on the Vedantu Website for free.

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NTA is responsible for the release of the JEE Main 2022 June and July Session cut off score. The qualifying percentile score might remain the same for different categories. According to the latest trends, the expected cut off mark for JEE Main 2022 June and July Session is 50% for general category candidates, 45% for physically challenged candidates, and 40% for candidates from reserved categories. For the general category, JEE Main qualifying marks for 2021 ranged from 87.8992241 for general category, while for OBC/SC/ST categories, they ranged from 68.0234447 for OBC, 46.8825338 for SC and 34.6728999 for ST category.
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FAQs on JEE Important Chapter - Biomolecules


1. What are the main points to remember while tackling problems involving biomolecules?

Students should practise drawing the ring structures of the biomolecules to remember the linkages between the molecules because most of the answers in biomolecules are based on these linkages. 

2. Do questions from the biomolecule chapter come every year in JEE Main?

yes, the biomolecule chapter is one of the important chapters that comes in JEE Main every year. This chapter is considered as a scoring chapter as the  topics under this chapter are very less and easy to understand. 

3. What is the weightage of this chapter in JEE Main?

Nearly 1-2 questions arise in the exam from this chapter covering about 4 marks which makes about 2% of the total marks.